GB2154917A

GB2154917A - Grinding wheel

Info

Publication number: GB2154917A
Application number: GB08424723A
Authority: GB
Inventors: Kenneth G Hall
Original assignee: ELGIN DIAMOND PROD
Current assignee: ELGIN DIAMOND PROD
Priority date: 1984-02-24
Filing date: 1984-10-01
Publication date: 1985-09-18
Also published as: GB8424723D0

Abstract

A grinding wheel which includes a flat disk of perforated metal and a cylindrical ring of perforated metal, both of which are integrally molded with a backing material and subsequently machined to expose the perforated metal. The flat disk and the cylindrical ring are proportioned and molded into the backing material such as to form intersecting surfaces 12,14 forming a corner around the edge and about the periphery of the grinding wheel. Abrasive materials then are bonded to the exposed perforated metal including the intersecting edge so as to provide a grinding wheel having a peripheral grinding edge, as well as a face grinding surface 12, a peripheral grinding surface 14, or both. <IMAGE>

Description

SPECIFICATION Grinding wheel This invention relates to an improved grinding wheel, and concerns an improved grinding wheel of the type having a face grinding surface, or peripheral grinding surface, formed by means of a flat disk of perforated metal, or a cylindrical ring of perforated metal, which is embedded in a backing material with the surface thereof exposed and having abrasive particles affixed on the exposed surfaces thereof. The invention also relates to an improved grinding wheel as described having intersecting grinding surfaces forming a corner about a peripheral edge of the grinding wheel so as to provide thereon at least one flat grinding surface and a peripheral grinding edge.

In U.S. Patent Specification No.

3,860,400, there is disclosed a grinding wheel including a backing material into which is embedded a metallic sheet so that portions of the metallic sheet are exposed, with abrasive particles bonded to the exposed portions of the metallic sheet to form or provide a grinding surface. While this patent teaches a method of providing a grinding surface on a grinding wheel, it does not disclose or teach how a peripheral grinding edge can be provided on a grinding wheel.

In the past, and presently, numerous grinding wheels have been manufactured and sold by the assignee of the present invention, under the trademark DYCLAD. These prior DYCLAD grinding wheels have had a grinding surface on the face of the wheel, or on the periphery of the wheel. However, none of these grinding wheels have both a face grinding surface and a peripheral grinding surface on the same grinding wheel. Furthermore, neither the face grinding surface nor the peripheral grinding surface extended around the corner of the peripheral edge of the grinding wheel so as to provide a peripheral grinding edge, i.e. a grinding edge disposed or partially disposed on both the peripheral surface and the face of the grinding wheel. The grinding wheels therefore do not permit a user to effectively "grind around the edge".

Grinding wheels fabricated in this fashion are far superior to other types of grinding wheels, particularly the older type of grinding wheels which were simply fabricated by bonding together abrasive materials. This type of grinding wheel, since it was simply fabricated of an abrasive material, had a peripheral grinding edge. The grinding wheels, however, and particularly the peripheral grinding edge, have a relatively short useful life in comparison to grinding wheels fabricated in accordance with the above-mentioned U.S. Patent 3,860,400 or the DYCLAD grinding wheels, and the peripheral grinding edge contantly required redressing to square the grinding edge. While these grinding wheels are far less acceptable than the newer ones, they do have this feature that many users desire and, for sometime, have sought on the newer grinding wheels.

Many attempts have been made to provide a peripheral grinding edge on these newer grinding wheels, however, none have been successful. In fact, until the advent of the present invention, it was generally considered by many to be impossible, or at least impractical from a standpoint of manufacturing an inexpensive grinding wheel, to provide such a peripheral grinding edge on these newer grinding wheels.

Accordingly, it is an object of the present invention to provide an improved grinding wheel having intersecting grinding surfaces forming a corner about the peripheral edge thereof so as to provide thereon a peripheral grinding edge, with the grinding surfaces being formed by metallic disks and rings embedded in the backing material with portions thereof exposed and having abrasive particles bonded thereto.

The above objective is accomplished by the grinding wheel of the present invention which includes a flat disk of perforated metal and a cylindrical ring of perforated metal, both of which are integrally molded with a backing material and subsequently machined to expose the perforated metal. The flat disk and the cylindrical ring are proportioned and molded into the backing material such as to form intersecting surfaces forming a corner around the edge and about the periphery of the grinding wheel. Abrasive materials then are bonded to the exposed perforated metal including the intersecting edge so as to provide a grinding wheel having a peripheral grinding edge, as well as a face grinding surface, a peripheral grinding surface, or both.

According to the invention there is provided a cylindrical grinding wheel having a flat face and a peripheral edge comprising: a backing material; a flat disk of perforated metal embedded within said backing material on the flat face thereof, said flat disk having one surface thereof exposed and having abrasive particles affixed to the exposed surface thereof; a cylindrical ring of perforated metal embedded within said backing material on the peripheral edge thereof, said cylindrical ring having one surface thereof exposed and having abrasive particles affixed to the exposed surface thereof; said flat disk and said cylindrical ring each having an edge thereof in mating engagement and providing intersecting surfaces forming a corner about a peripheral edge of said grinding wheel;; whereby at least one flat grinding surface and a peripheral grinding edge formed by said intersecting surfaces and extending around the corner at the peripheral edge of the grinding wheel is provided thereon.

Further, according to the invention there is provided a method of molding a cylindrical grinding wheel having intersecting grinding surfaces forming a corner about a peripheral edge thereof so as to provide thereon a peripheral grinding edge comprising the steps of: placing within a steel mold having a cylindrical cavity formed therein a flat disk and a cylindrical ring of perforated metal such that the edges thereof are in mating engagement and provide intersecting surfaces forming a corner; filling said cylindrical cavity with a molding compound and molding the same until said molding compound is cured to thereby provide a grinding wheel blank; removing said grinding wheel blank from said mold; machining said grinding wheel blank to expose a surface of said flat disk and said cylindrical ring; and affixing abrasive particles to the exposed surfaces of said flat disk and said cylindrical ring; whereby at least one flat grinding surface and a peripheral grinding edge which extends around the corner at the peripheral edge of the grinding wheel is provided thereon.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a grinding wheel exemplary of the invention; Fig. 2 is a sectional view taken along lines 2-2 of Fig. 1; Fig. 3 is a top plan view of the flat disk; Fig. 4 is a side plan view of the cylinder ring; Fig. 5 is a partial sectional view of the grinding wheel in accordance with one embodiment of the invention; Fig. 6 is a partial sectional view of the grinding wheel with a second embodiment of the invention; Fig. 7 is a partial sectional view of the grinding wheel in accordance with still another embodiment of the invention; and Figs. 8-10 are views generally illustrating the manner in which the grinding wheel is molded.

Referring now to the drawings, in Figs. 1 and 2 there is illustrated a grinding wheel 10 having a face grinding surface 1 2 and a peripheral grinding surface 1 4. The method of forming the grinding wheel 10 is more particularly described below, however, generally, the face grinding surface 1 2 is formed by embedding a flat disk 20 (Fig. 3) of perforated metal into a backing material 1 8 to form a grinding wheel blank (not shown). The grinding wheel blank then is machined to expose the surface of the flat disk 20, and abrasive particles such as diamond, cubic boron nitride or the like is afixed to the exposed surface of the flat disk 20 to form the face grinding surface 12.The peripheral grinding surface 14 likewise is formed by embedding a cylindrical ring 22 (Fig. 4) of perforated metal into the backing material 18, machining the grinding wheel blank to expose a surface of the cylindrical ring, and then bonding abrasive particles to the exposed surface of the cylindrical ring.

As indicated above, numerous grinding wheels have been manufactured and sold having either a face grinding surface 12, or a peripheral grinding surface 14. None of these grinding wheels have both a face and a peripheral grinding surface. Furthermore, none of these grinding wheels have a peripheral grinding edge.

In accordance with the present invention, a peripheral grinding edge 1 6 is provided on the grinding wheel 10 by embedding within the backing material 1 8 two grinding surfaces which matingly engage to provide intersecting grinding surfaces that form a corner about the peripheral edge of the grinding wheel. As illustrated in Fig. 2, these intersecting grinding surfaces can be formed by a flat disk 20 of perforated metal and a cylindrical ring 22 of perforated metal so as to provide in addition to the peripheral grinding edge 1 6 both a face grinding surface 1 2 and a peripheral grinding surface 14.Alternatively, the width of the flat disk 20 can be substantially reduced in size so that effectively only a peripheral grinding surface 1 4 and a peripheral grinding edge 1 6 is provided, with the flat disk being only of a sufficient width to still form intersecting grinding surfaces, as illustrated in Fig. 5. Conversely, the width of the cylindrical ring 22 can be reduced so as to effectively provide only a face grinding surface 1 2 and a peripheral grinding edge 16, with the cylindrical ring being only of a sufficient width to still form intersecting grinding surfaces, as illustrated in Fig. 6. Also, preferably and advantageously, for reasons set forth below, the flat disk and cylindrical ring are proportioned so that the edge of the ring abuts against the disk, as illustrated in Figs.

2, 5 and 6. It, however, is possible to proportion the disk and ring so that the peripheral edge of the disk abuts against the ring, as illustrated in Fig. 7. Also, a welding bead 24 (Fig. 7) can be applied to pre-assemble the disk and ring before molding the grinding wheel 10, however, it has been found that such a bead is not necessary, as far as structural integrity of the grinding wheel is concerned.

In fabricating the grinding wheel 10, the thickness of the perforated metal from which the flat disk 20 and the cylindrical ring 22 are formed may vary, however, it must be of a sufficient thickness in proportion to the num ber of holes formed in it that it remains relatively rigid. The perforated metal also should be open to provide swarf clearance and to assure free, cool cutting. Tests have established that the perforated metal should be open within a range of 2363%, with a preferred openess of 60%. Further tests have established that the perforated metal to function satisfactory and be open 63% should be a 1 6 gauge steel. Using a 1 6 gauge steel, the holes may be 5/32" (0.4 cm) in diameter staggered on 3/16" (0.48 cm) centres, thereby being 63% open.In providing a perforated metal which is 23% open, the holes may have a diameter of 1 /8" (0.32 cm) staggered on 1 /4" (0.64 cm) centres. A perforated metal which is open 63% and is of a lesser thickness may be operable, but it will not provide a satisfactory grinding wheel in terms of useful life since the perforated metal is not of sufficient durability to provide a functional product. By the same token, if the 1 6 gauge perforated metal is not open more than 23%, the metal is too rigid and tends to separate, deform or crack. Accordingly, while the thickness of the perforated metal may be less than 1 6 gauge, it is not sufficiently rigid to provide a durable wheel having an extended useful life if the perforated metal is open at the upper end of the range of openness desired, i.e. within the 6063% range.

If the range of openness is near the lower end of the range, using a thinner metal still fails to provide the desired durable wheel since the perforated metal is not of sufficient rigidity to withstand heavy use for any extended period and thus has a relatively short useful life in comparison to the heavier 1 6 gauge metal.

The perforated disk 20 and ring 22 after being integrally molded with the backing material 1 8 and being machined as more specifically set forth below have abrasive particles such as diamond or cubic boron nitride bonded to the exposed portions thereof to form the face grinding surface 1 2 and the peripheral grinding surface 1 4. The abrasive particles are bonded to the exposed portions in conventional fashion, as by electroplating.

As may be seen in Fig. 2, the perforated disk 20 and ring 22 form an intersecting surface or edge around or about the entire peripheral edge of the grinding wheel 10. When the abrasive particles are bonded to the perforated disk 20 and ring 22, the exposed portions thereof at the peripheral edge of the grinding wheel 10 also have abrasive particles bonded to it to thereby form the edge grinding surface 1 6. The perforated disk 20 and ring 22 both are discontinuous about the intersecting surface as a result of the holes formed in the perforated metal and the forming of the disk 20 and ring 22.This discontinuous intersecting surface functions to key together and form a strong bond between the backing material 1 8 and the perforated disk 20 and ring 22 about the edge grinding surface 1 6 to deter separation which enhances the useful life of the grinding wheel 10.

The backing material 1 8 is formed of a nonconductive material, and may be any suitable, moldable material which upon molding provides a machinable, strong, rigid grinding wheel blank. Any number of synthetic plastics may be used. A preferred material is a twostage phenolic heat resistant molding compound sold under the trademark PLENCO, by Plastics Engineering Company, Sheboyagan, Wisconsin.

The grinding wheel 10 may be molded in generally conventional fashion, depending upon the molding compound utilized for backing material 1 8. However, in molding the grinding wheel 10, the tolerances of the flat disk 20, the cylindrical ring 22 and the mold cavity are to a great extent critical in providing a satisfactory grinding wheel. Also, the manner in which the grinding wheel is finished likewise is critical, otherwise a grinding wheel which is less than satisfactory to provide an extended useful life will result.

In Figs. 8-1 0, there is generally illustrated a mold 40 and method for molding the grinding wheel 1 0. When using the above-identified PLENCO molding compound, a molding press (not shown) with a capacity of 75 tons (76,272 Kg), equipped with electrically heated top and bottom platens with a temperature capability of 375"F (190"C) minimum preferably is used. The mold 40, as illustrated, includes a mold body 42 having a cylindrical cavity 44 extending through it. A cylindrical core 46 is disposed axially within the cylindrical cavity 44, and is slidably disposed in a mold base 48. The mold base 48 seals the bottom of the cylindrical cavity 44, and is movably disposed therein.In this instance, the mold base 48 has a raised diameter portion 50, for providing on the molded grinding wheel blank 52 (Fig. 10) a recessed inner face 54. The mold 40 also includes an upper mold portion 56 which is movable into the cylindrical cavity 44, and also has a cylindrical bore 58 extending through it for receiving therethrough the cylindrical core 46.

The procedure in molding the grinding wheel blank 52 is as follows. Initially, the mold body 42 and cylindrical core 46 are blocked using, for example, blocks 58-60, to provide as much mold depth as possible in the cylindrical cavity 44. A mold release is applied to the mold surfaces which will be contacted by the molding compound.

The flat disk 20 is placed in the cylindrical cavity 44 atop the mold base 48. The tolerance of the flat disk 20 and the cylindrical cavity 44 must be such that the peripheral edge of the flat disk makes a tight slide fit with the cavity wall, around its entire periphery. The cavity wall functions as a common plane to the flat disk 20 and the cylindrical ring 22 to control tolerance, to thereby assure that the intersecting surfaces forming a corner at the peripheral edge of the finished grinding wheel. The cylindrical ring 22 next is placed in the cylindrical cavity 44, with its lower peripheral edge abutted against the flat disk 20, as illustrated. The tolerance of the cylindrical ring 22 also is such that it makes a tight, slide fit with the cavity wall, around its entire periphery.Again, the cavity wall being a common plane controls the tolerance of the cylindrical ring 22 and provides a readily detectable indication of whether proper tolerances are observed.

The mold 40 then is filled with an amount of molding compound which will provide a grinding wheel blank with the backing material 1 8 extending over the top of the cylindrical ring 22 (as shown) by approximately 1/16" (0.16 cm), when the molding cycle is completed. The amount of material, of course, varies depending upon the diameter and thickness of the grinding wheel 10, but can be easily determined by measuring and testing the compression of the molding compound during molding.

After loading the mold 40 with the molding compound, the upper mold portion 56 is installed and the mold assembly is cold pressed using an arbor press (not shown) to remove entrapped air, as illustrated in Fig. 9.

The mold assembly then is transferred to the molding press (not shown). The upper and lower platens on the molding press should be pre-heated and maintained at a temperature of 375"F (190 C) minimum, at the time of transferring the mold assembly to the molding press. The blocks 58-60 are removed, and a molding pressure of 50 tons (50,848 Kg) is applied, and maintained, until a mold temperature of 340'F (171 or) is attained, indicating that the molding cycle is complete.

The mold assembly is removed from the mold press, allowed to cool, and then the grinding wheel blank 52 is removed from the mold.

After molding, and prior to plating the grinding wheel blank 52 with abrasive particles, the arbor hole 11 (Fig. 1) is bored, again maintaining an established tolerence.

Next, using the arbor hole 11 as a reference, the backside of the grinding wheel blank 52, i.e. the side thereof opposite that containing the flat disk 20, is machined to absolute flatness and squareness. The peripheral surface of the grinding wheel blank 52 is then machined, using the arbor hole 11 as a reference, to establish a true indicated radius within an established tolerance. The radius is such that the surface of the perforated metal forming the cylindrical ring 22 is exposed.

The grinding wheel blank 52 is then machined, using the arbor hole 11 as a reference to expose the surface of the perforated metal forming the flat disk 20 and to establish a true indicated radius of an established tolerance. The edge of the intersecting grinding surfaces 1 2 and 14 preferably is slightly rounded by machining it.

After machining the grinding wheel blank 52 in the above-described fashion, the exposed surfaces of the flat disk 20 and the cylindrical ring 22, including the intersecting edges thereof, next are plated with abrasive particles. Preferably diamond grit is used, however, other abrasive particles such as cubic boron nitride and the like can be used.

Prior to the plating, the exposed surfaces of the flat disk 20 and the cylindrical ring 22 are chemically cleaned. The abrasive particles are bonded to the exposed surfaces in conventional fashion, as by electroplating, in which case a bright nickel plating bath is used. The exposed surfaces are pre-plated, the abrasive particles tacked to the exposed surfaces, and then plated out to provide 5070% plating depth relative to the single layer of abrasive particles.

After plating, the grinding wheel 10 is dynamically balanced to an accuracy within 1 gram maximum out-of-balance.

As indicated above, the wall of the mold cavity 44 forms a common plane of reference for the flat disk 20 and the cylindrical ring 22 to control tolerances. If the tolerance of the outer diameter of the cylindrical ring 22 relative to the wall of the mold cavity 44 is not maintained, the grinding wheel 10 will be less than acceptable. If the outer diameter is larger than tolerance, a separation of the cylindrical ring 22 from the backing material 1 8 will occur in use of the grinding wheel 10. The extent of separation will be directly proprotioned to the amount of out-of-tolerance average. If the outer diameter is smaller than tolerance, when the periphery of the grinding wheel blank 52 is machined to expose the cylindrical ring 22, the thickness of the cylindrical ring 22 on one side of the grinding wheel 10 will be reduced.The amount of reduction in the thickness of the cylindrical ring 22 will be twice the rate of decentration.

The reduction in thickness may cause breakage of the cylindrical ring 22 during use of the grinding wheel 10.

If the tolerance of the outer diameter of the flat disk 20 relative to the wall of the mold cavity 44 is larger than tolerance, the flat disk 20 cannot be installed properly in the mold cavity, and will not be flat. If the tolerance is smaller, the critical intersecting edge of the grinding surfaces will not be formed properly.

Also, if prior to the plating, the flat disk 20 and cylindrical ring 22 are not machined relative to the arbor hole 11 to the true indicated radius tolerances, the effectiveness of the resultant plated surfaces will be substantially reduced for the user. The amount of reduction will be directly proportioned to the out-of-tolerance average. Further still, if the grinding wheel 10 is not dynamically balanced to the required accuracy, the effectiveness of the grinding wheel 10 will be substantially reduced, the reduction again being directly proportioned to the out-of-tolerance average.

Claims

1. A cylindrical grinding wheel having a flat face and a peripheral edge comprising: a backing material; a flat disk of perforated metal embedded within said backing material on the flat face thereof, said flat disk having one surface thereof exposed and having abrasive particles affixed to the exposed surface thereof; a cylindrical ring of perforated metal embedded within said backing material on the peripheral edge thereof, said cylindrical ring having one surface thereof exposed and having abrasive particles affixed to the exposed surface thereof; said flat disk and said cylindrical ring each having an edge thereof in mating engagement and providing intersecting surfaces forming a corner about a peripheral edge of said grinding wheel;; whereby at least one flat grinding surface and a peripheral grinding edge formed by said intersecting surfaces and extending around the corner at the peripheral edge of the grinding wheel is provided thereon.

2. A cylindrical grinding wheel according to Claim 1, wherein said intersecting surfaces forming the corner are perpendicular to one another.

3. A cylindrical grinding wheel according to Claim 1 or 2, comprising a flat grinding surface on the flat face of said grinding wheel and a flat grinding surface on the peripheral edge thereof.

4. A cylindrical grinding wheel according to Claim 1 or 2, wherein said intersecting surfaces provide a flat grinding surface of the flat face of said grinding wheel and form a corner which extends only a short length on the peripheral edge of said grinding wheel.

5. A cylindrical grinding wheel according to Claim 1 or 2, wherein said intersecting surfaces provide a flat grinding surface on the peripheral edge of said grinding wheel and form a corner which extends only a short length on the flat face thereof.

6. A cylindrical grinding wheel according to Claim 1, wherein the mating engagement of said flat disk and said cylindrical ring is between a peripheral edge of said cylindrical ring and the surface of said flat disk opposite the exposed surface thereof.

7. A cylindrical grinding wheel according to Claim 1, wherein the mating engagement of said flat disk and said cylindrical rings is between the edge of said flat disk and the surface of said cylindrical ring opposite the exposed surface thereof.

8. A method of molding a cylindrical grinding wheel having intersecting grinding surfaces forming a corner about a peripheral edge thereof so as to provide thereon a peripheral grinding edge comprising the steps of: placing within a steel mold having a cylindrical cavity formed therein a flat disk and a cylindrical ring of perforated metal such that the edges thereof are in mating engagement and provide intersecting surfaces forming a corner; filling said cylindrical cavity with a molding compound and molding the same until said molding compound is cured to thereby provide a grinding wheel blank; removing said grinding wheel blank from said mold; machining said grinding wheel blank to expose a surface of said flat disk and said cylindrical ring; and affixing abrasive particles to the exposed surfaces of said flat disk and said cylindrical ring, whereby at least one flat grinding surface and a peripheral grinding edge which extends around the corner at the peripheral edge of the grinding wheel is provided thereon.

9. A method according to Claim 8, wherein the wall of said cylindrical cavity provides a ccmmon plane for controlling tolerances, said flat disk and said cylindrical ring each having an outer diameter to provide a tight slide fit relative to said wall, whereby the edges thereof are in mating engagement and provide intersecting surfaces forming a corner.

1 0. A method according to Claim 8 or 9, further comprising the steps of boring an arbor hole in said grinding wheel blank to a prescribed tolerance; machining said grinding wheel blank on the side thereof opposite said flat disk to absolute flatness and squareness; machining the peripheral surface of said grinding wheel blank to establish a true indicated radius of a prescribed accuracy; and machining the side of said grinding wheel blank containing said flat disk to establish a true indicated radius of a prescribed accuracy.

11. A method of Claim 8, 9 or 10, further comprising the step of: slightly rounding the intersecting edges of said flat disk and said cylindrical ring.

12. A method of Claim 8, 9, 10 or 11, further comprising the step of: dynamically balancing the grinding wheel after affixing thereto said abrasive particles to a prescribed out-of-balance accuracy.

1 3. A method of molding a cylindrical grinding wheel substantially as hereinbefore described with reference to the accompanying drawings.

14. A cylindrical grinding wheel substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.